A commercial telecommunications network operated by a service provider typically supports voice and/or data communications between various customer locations served by the network. An overall communications system may be subdivided into an access network and a core network, which may or may not be owned and operated by different service providers. Generally, customer devices communicatively couple to the access network which, in turn, connects to the core network. The access network includes what many people refer to as “the last mile,” that is, the connectivity from a customer location, such as an office building, to a point where a service provider has significant facilities, such as a metro hub or a “service edge” at the periphery of the core network. In contrast to the access network, the core network usually provides transport of large aggregate flows over long distances and handles the selective routing of each customer's voice and data traffic to other locations served by the network. The access network generally comprises a series of switches, aggregators, multiplexers, demultiplexers, routers, hubs, and the like, which provide connectivity between the customer's equipment and the core network.
FIG. 1 illustrates an example of a prior art access network 100 in which a customer (i.e., an end-user of telecommunications services, not shown), located in one or more office buildings 110, 120, or 130, may connect to a service edge 165 and onto the various service networks, designated by service networks 170, 180 and 190. In the example access network diagram 100, the access network may comprise metro node 150, a Local Exchange Carrier (LEC) 140, and a metro/long-distance (LD) hub 160.
Typically, the customer's equipment may comprise many devices, such as routers, hubs, workstations, Ethernet switches, or the like. In the example shown, these devices may comprise an Ethernet device, frame relay (FR) or asynchronous transfer mode (ATM) devices, etc. A customer's devices are often collectively referred to as customer premise equipment (CPE). For example, in a typical environment such as building 110, the CPE may be an Ethernet device 111. Ethernet device 111 may be connected to add/drop multiplexer (ADM) 112, wherein ADM 112 may be part of the service provider network. ADM 112 serves to aggregate lower bandwidth services from one or more customers for transmission over a larger bandwidth link, or pipe, illustrated by the TDM based SONET OC-N connection 155. For purposes of efficiency, the service provider often designs its network so that smaller volumes of communications traffic flow into tributaries to be combined with other similar sized flows to form larger aggregate flows. Progressively larger aggregate flows leverage economies of scale and justify extremely high-bandwidth communications in the core network (not shown). These high-bandwidth communications are much easier and more cost effective to maintain and control than a large number of smaller bandwidth resources would be individually, particularly over very long distances.
An access network 100 is typically viewed as a conduit to deliver raw traffic to a service edge. For this simple purpose, TDM links are traditionally used to fulfill the needs of all types of traffic. TDM communications links, such as the common T1 or DS3 access links, have been commonplace for many years and are a very familiar legacy of traditional telephone technology. As business data communications needs have emerged, especially over the last two decades, a TDM link has been the principal way of delivering customer traffic to the service provider's “doorstep,” the service edge. By design, the TDM communications link is well-suited for handling inherently constant bit rate communications and more recently has been adapted for carrying packet-oriented traffic such as Ethernet traffic. With some adaptations, such as inverse multiplexing, channels of a TDM link may even be used for carrying ATM or frame relay traffic. When a TDM link is used in this manner, it is essentially a passive communications conduit between exactly one customer or site and the service provider edge. Each customer usually arranges their own access through a dedicated T1 line to the service edge. The dedicated T1 line is often reserved for the given customer and entirely paid for by that customer, whether directly or indirectly.
In the example access network diagram 100, a customer in building 110 needs to connect Ethernet (111) and frame relay (114) services onto the access network. In a traditional TDM based access network, a higher bandwidth OC-3 or OC-12 link (155) is connected to an ADM 112 in the building. The ADM serves to de-multiplex the larger bandwidth OC-N link into multiple DS3 links, one of which connects ADM 112 to Ethernet device 111. A customer needing frame relay service 114 may connect to the network through a T1 line provided by an M13 multiplexer 113, which converts the DS3 link from the ADM into multiple T1 links.
Customers in buildings 120 and 130 may access the network via DS3 or T1 lines that have been leased from a telephone company, as represented by local exchange carrier (LEC) 140. The LEC then may aggregate the multiple TDM based links from multiple customers into a higher bandwidth link, perhaps an OC-N based link, before passing it onto the metro node 150. Otherwise, LEC 140 may simply couple customer sites to metro nodes via individual T1/DS3 connections. The metro node 150 then further aggregates and grooms the smaller communications traffic flow into tributaries to form larger aggregate flows, using, for example, ADM's 151, digital cross connects 152 and a fiber distribution frame 153. The larger aggregate flows 159 are passed on to a metro/LD hub 160, where the traffic is processed for distribution to other service networks, e.g., service networks 170, 180 and 190, and to the core network (not shown). The metro/LD hub 160 may also use a collection of ADMs 164, digital cross connects 162, a fiber distribution frame 163, and one or more switches or routers 161.
Provisioning to establish new communications or make changes to existing communications in an access network in accordance with the prior art is often burdensome and time-consuming. Providing new services or additional bandwidth to a customer typically involves submitting service order tickets to an incumbent local exchange carrier and/or performing manual patching of cables in the service providers' sites and often at a customer site as well. One of the major inefficiencies of an access network lies in provisioning a customer's access link(s) for service. Provisioning often involves a great deal of manual cable patching at various sites, along with configuring a variety of equipment, including the various ADMs, crossconnects, switches, etc. In a typical scenario, it is not unusual for a path between a customer site and a service edge to comprise more than 20 “touchpoints,” that is, places where a cable must be manually plugged in or equipment must be manually configured in some way.
Furthermore, traditional approaches have required meticulous handling of separate flows which involves manpower and extra multiplexing and switching equipment. For example, it is common to provide ATM services to a customer by using four DS-0 TDM circuits in an inverse multiplexing arrangement. This means that, in addition to transferring ATM traffic to TDM traffic using special equipment at the customer end, the separate DS0 circuits must each be managed, provisioned and groomed in the service provider's network to reach their proper common destination. These complicated manipulations are a consequence of fitting ATM onto the common TDM transport signals.
Additional equipment and communications links are also necessary to provide operations personnel visibility into an access device which is typically located at a customer premise. In an “off-network” situation, it is frequently necessary to have a separate T1 or DS3 communications link (or at least a separate telephone line) from the service provider to the access device or other equipment located in the customer's building. A multiplexer and/or router would receive the communications link and isolate the channel used for maintenance and control and route that channel to an access device. This type of configuration creates an out-of-band maintenance and control channel that requires additional equipment and physical set-up. Additionally, because a separate T1 communications link is utilized for relatively simple low-bandwidth maintenance and control communications, the out-of-band maintenance control channel is wasteful and expensive.
Thus, a primary concern for network providers is simplifying and reducing the burden of monitoring, control and provisioning of network elements in an access telecommunications network.